1. Field of the Invention
The present invention relates to a tact switch in which a plurality of separate contacts may be electrically connected together with a small transmission path via operation on the tact switch.
2. Description of Prior Art
Tact switches which quickly respond to a manual depression have been used in many appliances, such as in telephone sets, microwaves, remote controls, and TV sets. JP Pat. No. 2572590 discloses an electrical switch which includes a housing, a plurality of contacts retained in the housing; a metal dome lying over the plurality of contacts, an actuator arrangement and a cover with an oblique plate. The actuator arrangement includes a press section positioned between the cover and the metal dome and a manipulating section which extends to external side of the housing. In operation, when the manipulating section of the actuator arrangement is pressed by a user, the press section of the actuator arrangement moves forwardly and engages with the oblique plate, at the same time the oblique plate drives the press section downwardly to depress a middle portion of the metal dome so that the metal dome simultaneously electrically connects the plurality of contacts to each other. However, after a period of use, the metal dome can be elastically deformed through enough cycles that it will fail through metal fatigue, which makes the tact switch lose switch function. Moreover in the above prior art, a distance between the metal dome and the contacts is too large such that, in operation, the metal dome will be distorted to such an extent which results in a longer response time of the tact switch.
Hence, an improved tact switch is desired to overcome the disadvantages of the prior art.
A main object of the present invention is to provide a tact switch providing a reliable electrical connection among a plurality of contacts.
Another object of the present invention is to provide a tact switch having a shortened response time.
A tact switch in accordance with the present invention comprises an insulative housing, a plurality of fixed contacts, a movable contact, an actuator and a top cover. The insulative housing has a bottom wall and peripheral walls extending upwardly from the bottom wall. The plurality of fixed contacts are retained in the bottom wall of the insulative housing. Each fixed contact has a contact portion exposed to an inner surface of the bottom wall of the insulative housing and a soldering portion soldered to a printed circuit board. The top cover is mounted on the housing and has an engaging plate projecting downwardly therefrom. The movable contact is positioned above the fixed contacts and has a plurality of projections projecting therefrom for engaging with the plurality of contact portions of the plurality of fixed contacts. The actuator having an operating portion extending to external side of the insulative housing and a press portion slideably mounted between the top cover and the movable contact.
In operation, when the actuator is pressed inwardly, the press portion of the actuator engages with the engaging plate, at the same time the engaging plate drives the press portion downwardly to depress the movable contact, which elastically deforms downwardly until the plurality of projections contact with the plurality of contact portions so that the movable contact simultaneously electrically connects the plurality of fixed contacts to each other, achieving an electrical connection between the plurality of fixed contacts. When the operating portion is released, the engaging plate urges the actuator to move outwardly from the housing and at the same time releases the moveable contact to make the plurality of projections out of electrical contact with the plurality of contact portions.